The present invention refers to an apparatus for comminuting sheet metal or similar material, and in particular to a crusher having a housing frame for supporting a rotor, formed as a striking tool, for rotation about an axis and interacting with an enveloping deck in the form of a grate assembly provided with holes or an abrasive plate assembly provided with depressions.
An apparatus of this type, including hammer mills, are typically used for crushing scrap of motor vehicles. Generally, the material is fed via a sloped track into the rotor compartment of the crusher and subsequently comminuted and pulverized between the striking tool and the enveloping deck. In a hammer mill, material is crushed by a plurality of hammers which are secured on the rotating rotor, and is subsequently ejected from the mill through holes formed in the grate assembly.
Abrasive plates may also be utilized in combination with the grate assembly in mills, sifters, sorters and processing plants, and either cast or made from rolled sheet metal. At operation, the enveloping deck, i.e. abrasive plates or grates are subject to extremely high stress by the material being comminuted which transmits forces onto the abrasive plates from different directions. In particular, certain areas of the housing bottom are subject to maximum stress as a result of frictional loads, crushing action and pressure loads generated between the bottom and the hammers. Thus, single grates or abrasive plates are subject to a comparably greater wear and have a reduced service life as other parts of the deck. This wear as a result of the great force transmitted by the striking tool onto the grates or abrasive plates causes a stretching of the grates and abrasive plates and lead to an elongation of the holes or depressions. This expansion of the grates and abrasive plates impairs their attachment to the apparatus and especially complicates a dismantling thereof. A dismantling is frequently required when the grates or plates become wedged in the apparatus. When this happens, the grates or plates can be dismantled only through use of a welding torch which usually results in a complete destruction of these parts. A desired, frequent replacement of the grates or plates for producing different materials, i.e. exchange of only partially worn out plates for later reuse and for variation of the hole sizes is not possible to date.